Beverages are typically packaged into cans, bottles (glass or plastic) and other containers using high speed blending and filling systems. Various product components (e.g., water and a syrup) are blended together in precisely controlled amounts to provide a “product blend” that is subsequently filled into containers. Carbonated beverages such as soft drinks further include a carbonation step between the blending and filling stages, wherein CO2 is dissolved into the beverage. These processes are usually performed at high speeds, requiring precise control of various parameters such that even a small deviation in one process condition can reduce throughput or result in deleterious effects on the process and/or the packaged beverage.
For example, levels of air (as dissolved oxygen and nitrogen) within the product blend generally should be as low as possible. If the levels of dissolved oxygen and/or nitrogen are too high, excessive foaming will occur during filling—especially with carbonated beverages. This not only results in excessive product loss and short fills, but also typically requires slower line speeds and/or filling at reduced temperatures in an attempt to limit foaming caused by air in the product blend.
In addition to causing foaming during container filling, dissolved air can be problematic after packaging. For example, high levels of oxygen can cause corrosion of the container (particularly metal cans) as well as product degradation, thereby reducing the shelf life of the packaged beverage.
In a typical beverage, e.g., a carbonated beverage such as a soft drink, “syrup” is blended with process water according to product specifications to provide a product blend. If appropriate for the particular beverage being produced, the product blend is then carbonated prior to filing containers. As used herein, the term “syrup” means any concentrated flavoring composition that is combined with water to form a potable beverage. Syrups, particularly those used in the production of soft drinks, are typically of a higher viscosity than water. Syrups generally include a small amount of water to facilitate manufacture of the syrup, as well as blending (e.g., so the syrup can be metered and delivered to a blending stage for blending with process water). Syrups are typically mixtures of several ingredients, including one or more flavoring components, sweeteners (e.g., sugar) and other functional additives. In other instances, the syrup for a particular beverage comprises only a flavoring component(s) and water.
In filling beverages into containers such as cans or bottles, containers are conveyed to a filling machine where the product blend is dispensed into individual containers that are then sealed (e.g., a lid or cap is joined to the filled container). The product blend is delivered into the container at a relatively high pressure (e.g., 50 to 70 psig, or 1.5 to 2 times the saturation pressure for the targeted CO2 volumes of a carbonated beverage at the filling temperature). These high pressures not only maintain the CO2 in solution (i.e., dissolved), but also any air that is present in the product blend. The container is then vented to atmosphere just prior to being sealed closed (e.g., by capping in the case of bottles, or by seaming a metal lid onto cans). High-speed filling machines—especially when dispensing carbonated beverages—typically produce some amount of foam when the filled, pressurized container is vented. Foam is produced by the release of air (dissolved oxygen and nitrogen) that is present in the product blend. The pressure drop from venting causes the dissolved air to come out of solution. When too much oxygen and/or nitrogen is present in the product blend, excessive foaming will occur. This results in spillage (i.e., product loss) and incomplete filling (“short fill”) of the container. In order to reduce foaming, manufacturers typically will reduce the filling rate in order to limit agitation of the product (thereby slowing the entire production process) and/or run their filling system at lower temperatures (since the solubility of oxygen and nitrogen in the product blend increases as the temperature decreases).
Foaming can be especially problematic in the packaging of carbonated beverages. After blending of process water and syrup according to predetermined product specifications (i.e., a product recipe), the product blend is carbonated prior to bottling. Carbonation provides fizz (bubbles) that many consumers enjoy, as well as enhanced flavor (the carbon dioxide forms carbonic acid, which counteracts the sweetness of the soft drink). The level of carbonation is dependent upon the product recipe, which specifies the desired carbonation level for that product. Carbonation levels can vary significantly from one product to another, with beverages being produced at higher and higher carbonation levels. These higher carbonation levels result in even more foaming, as the higher amount of CO2 in solution will force out even more air which in turn causes additional agitation of a product that is more volatile (due to the increased level of CO2).
In order to reduce foaming as well as other problems resulting from too much air in the product blend, the process water is typically deaerated prior to being blended with syrup in order to reduce the levels of dissolved oxygen and nitrogen in the water. Process water is usually deaerated by vacuum deaeration or membrane deaeration, with the oxygen level typically reduced to 0.7 to 1.5 ppm and the nitrogen level typically reduced to 1.5 to 3 ppm before the process water is blended with syrup to form the product blend.
Although syrups also contain dissolved oxygen and nitrogen, deaerating syrup is problematic. For example, vacuum deaeration of the syrup is usually not feasible since it will result in significant losses of syrup components, especially more volatile components such as flavoring agents. In addition, since most syrups are highly concentrated, they tend to have a high viscosity, which is incompatible with conventional deaeration processes. Deaerating syrups also results in excessive foaming. In addition, the highly concentrated nature of syrups means that extensive and time-consuming cleaning of deaeration equipment would be necessary in order to remove residual flavoring agents and other syrup components between runs of different products. Because of these and other issues, typically only the process water used in final blending is deaerated in beverage manufacturing. However, syrups can have as much as 6-12 ppm of dissolved oxygen and up to 20 ppm dissolved nitrogen, and the addition of the process water introduces even more air into the product blend prior to packaging. Thus, even when produced with deaerated process water, product blends typically contain 1.5 to 2.5 ppm oxygen and 2 to 5 ppm nitrogen prior to carbonation.
As noted previously, excessive foaming is particularly problematic when bottling carbonated beverages. Carbonation is measured in volumes: a relative measurement of the volume of CO2 that is dissolved in one volume of the carbonated product. In this measurement, the “volume” of dissolved CO2 is the volume that dissolved gas would occupy at atmospheric pressure (1 atm) and 0° C. For example, 4 volumes of CO2 correlates to 4 liters of CO2 dissolved in one liter of carbonated product. The amount of CO2 that can be dissolved in a given quantity of liquid (i.e., CO2 solubility) depends not only on the nature of that liquid, but also its temperature and the partial pressure of CO2 in the gaseous atmosphere in contact with the liquid (i.e., Henry's Law). This relationship allows one to determine how much CO2 can be maintained in solution in a given liquid at a particular temperature and pressure, using a predetermined CO2 solubility table such as shown in FIG. 1 (or other predetermined data set or mathematical approximation). It should be noted that the CO2 solubility table in FIG. 1 is for water. However, such tables are sufficient for use in carbonating most beverages, and their use is standard in the beverage industry.
From the predetermined carbonation level for a particular product, the required saturation pressure (i.e., the CO2 pressure above the liquid that is required dissolve and maintain a specified amount of CO2 in solution) can be calculated from a chart similar to FIG. 1 (or other predetermined data set or mathematical approximation) for any given temperature. Such a table or other data set or mathematical approximation indicates the amount of pressure (as CO2) required to keep the CO2 absorbed in the liquid relative to the temperature of the product for various carbonation levels. As shown by the chart of FIG. 1, a greater volume of CO2 gas will dissolve in a cold liquid under high pressure. It is also well known that oxygen and nitrogen are significantly less soluble than CO2 in water. At 20° C. and one atmosphere, for example, the solubility of oxygen in water is about 2% that of CO2, and the solubility of nitrogen in water is about 1% that of CO2. This same relationship is true in water-based beverages comprising process water blended with syrup (wherein the volume of process water in the blend is significantly greater than the volume of syrup), such as soft drinks.
Existing processes for carbonating beverages typically operate at pressures from 35 to 80 psig in order to allow for complete absorption of the desired volume of CO2 gas (as specified for the product). The carbonated product is stored in a pressurized (with CO2) product tank for distribution to the filling equipment. The pressure at which the carbonated product is stored is generally greater than the saturation pressure requirement for the product with the specified carbonation level in order to maintain the CO2 dissolved in the product blend even if there are temperature variations. Typically, carbonated beverage product storage tanks operate at 1.5 to 2 times the calculated saturation pressure in order to not only maintain the CO2 in solution, but also to assist in the filling process. Also, the carbonated product is usually stored for only a few minutes prior to filling, and therefore any additional carbonation absorbed from the headspace in the storage tank is minimal.
Due to the operating pressures used in the carbonation process in order to meet product specifications as well as the increased pressure required by the filling equipment, oxygen and nitrogen are retained in the product blend during carbonation. However, when the pressure drops during post-fill venting prior to sealing, the oxygen and nitrogen dissolved in the product are released, thereby producing foam.
While a variety of systems and methods may exist for deaerating beverages prior to packaging, it is believed that no one prior to the inventors have made or used an invention as described herein.
The drawings are intended to illustrate rather than limit the scope of the present invention. Embodiments of the present invention may be carried out in ways not necessarily depicted in the drawings. Thus, the drawings are intended to merely aid in the explanation of the invention. Thus, the present invention is not limited to the precise arrangements shown in the drawings.